The sample strata for sampling errors defines the pairings or groupings of primary sampling
units used in the calculation of sampling errors when using the Taylor series expansion
method (for example, with the package Clusters).

Case identification uniquely identifies each household. In most surveys this is constructed
by concatenating the cluster or sample point number and the household number, but in some
surveys this may be the questionnaire number taken from the front page of the questionnaire

Cluster number is the number identifying the sample point as used during the fieldwork.
This variable may be a composite of several variables in the questionnaire. If so, the nonstandard
variables are included in RECH3 as country-specific variables.

Sample weight is an 8 digit variable with 6 implied decimal places. To use the sample
weight divide it by 1000000 before applying the weighting factor. All sample weights are
normalized such that the weighted number of cases is identical to the unweighted number of
households when using the full dataset with no selection. This variable should be used to
weight all tabulations produced using the data file. For self-weighting samples this variable
is equal to 1000000.